Product and process

ABSTRACT

A process is disclosed for reducing the noise level created when a compressive load is placed on a bonded reticulated batt of randomly arranged pneumatic closed-cell foamed fibers so as to flex the fibers. The reduction is achieved by coating the batt, prior to coating it with an adhesive binder, with an antiadhesive which is a selected polysiloxane, a selected polyoxyethylene polyoxypropylene glycol or a selected alkyl sodium sulfonate. The anti-adhesive prevents formation of weak bonds between the fiber and the adhesive which have been found to be the source of the noise (created when the weak bonds break) but does not prevent the formation of the usual strong bonds between the fiber and the adhesive.

[mite t-tes atet 1 1 Schick I [73] Assignee: E. 1. du Pont de Nemours &Co.,

Wilmington, Del.

[22] Filed: May 24, 11973 [21] Appl. No.: 363,664

[52] US. Cl. 117/76 FB, 117/76 T, 117/104 R, l17/138.8 F, 117/140 A,161/92, 161/155,

161/156 51 1111. c1. B44d 1/08, B44d H16 [58] Field 01 Search 117/140 A,76 FB, 76 T, 117/98, 138.8 F, 104 R; 161/92, 155, 156; 252/8.7, 8.9

[56] References Cited UNITED STATES PATENTS 2,677,700 5/1954 Jackson eta1. 252/89 X 3,381,077 4/1968 Bonner 264/321 3,402,070 9/1968 Brudmann 1l17/l38.8 3,461,026 8/1969 Schick 161/154 3,485,711 12/1969 Fish eta1.... 161/150 3,535,181 10/1970 Yunan 156/181 14 1 Feb. 18,1975

OTHER PUBLICATIONS Schick, Nonionic Surfactants, Pub. 1967 by MarcelDekker, Inc., New York, pages 309, 310, 312, 320, 350-352.

Primary Examiner-Leon D. Rosdol Assistant Examiner-Harris A. Pitlick[57] ABSTRACT A process is disclosed for reducing the noise levelcreated when a compressive load is placed on a bonded reticulated battof randomly arranged pneumatic closed-cell foamed fibers so as to flexthe fibers. The reduction is achieved by coating the batt, prior tocoating it with an adhesive binder, with an antiadhesive which is aselected polysiloxane, a selected polyoxyethylene polyoxypropyleneglycol or a selected alkyl sodium sulfonate. The anti-adhesive preventsformation of weak bonds between the fiber and the adhesive which havebeen found to be the source of the noise (created when the weak bondsbreak) but does not prevent the formation of the usual strong bondsbetween the fiber and the adhesive.

5 Claims, N0 Drawings FIELD OF THE INVENTION This invention relates tothe reduction of noise in fibrous cushioning structures when they areflexed under load. More specifically, this invention is directed to suchnoise-reduction in nonwoven batts of pneumatic foamed closed-cell fibersby coating the batts with a selected anti-adhesive prior to theapplication of an adhesive binder.

BACKGROUND Numerous types of foamed polymeric materials are used forcushioning applications. Among them are closed-cell microcellular foamedfibers in which the cells are inflated with an inflatant that isimpermeant to the cell walls and thus is confined within the cells,making the fibers permanently pneumatically resilient. These fibers,referred to herein as microcellular, inflated closed-cell pneumaticfibers, are made of synthetic organic polymers. They can be used toprepare reticulated batts in which the fibers are randomly arrangedwithin the batt and contact one another frequently at crossover points.To aid dimensional stability these batts are usually treated with anadhesive binder. These preparations are described in U.S. Pat. Nos.3,461,026; 3,485,711; 3,535,181; and 3,381,077, inter alia.

As stated above, to aid the dimensional stability of the batts, thebatts are usually subjected to an adhesive binder which infiltrates thebatt and binds the fibers therein at their crossover points. The battsare useful as cushioning structures for a variety of purposes, such aspillows or as an overlayer on mattress springs. However, when flexedunder a load, these bonded batts emit an auditory signal, or noise,which is objectionable to the ear, being a crackling noise.

It is believed that the noise is due to the breaking of weak bondsbetween the fibers in the batts and the adhesive binder, and it has nowbeen discovered that, by applying a mild anti-adhesive to the battbefore the adhesive binder is applied, these weak bonds can be preventedfrom forming. Thus, the objectionable crackling heard when the batts arestressed under load can be reduced by the use of the anti-adhesive. Aprocess involving its use comprises the process of this invention.

SUMMARY OF THE INVENTION This invention provides a process for reducingthe noise in compressible fibrous structures when flexed under stress,which comprises:

spraying a reticulated batt of randomly arranged, mi-

crocellular, inflated closed-cell, pneumatic fibers of a syntheticorganic polymer with between about 0.03 to about percent by weight basedon the weight of the fibers of an anti-adhesive composition comprising apolyoxyethylene polyoxypropylene polymethylsiloxane containing about 51%polyoxyethylene, a sodium alkylsulfonate of 22 to 24 carbon atoms, or apolyoxyethylene polyoxypropylene glycol containing about 80% po1yoxyethylene;

coating said sprayed batt with an adhesive binder comprising an aqueousemulsion of at least 40% by weight of an ethylene/vinyl acetatecopolymer wherein the vinyl acetate comprises 18-40% by weight of thepolymer; and

2 drying the coated batt.

DESCRIPTION OF THE INVENTION The batts used in the process of thisinvention are re ticulated structures containing the microcellular,inflated closed-cell, pneumatic filaments laid down on top of oneanother to obtain numerous crossings offilament portions and penetrationof portions of filaments at one thickness level into adjacent thicknesslevels. Individual filaments in the batt will vary in configuration fromstraight to curved to S shaped. An uncompressed batt may contain 3 to 40x./sq. yd. of the filaments. Ordinarily, the batts are obtained bylaying the filaments down on a horizontal surface and building up layersuntil the desired thickness is obtained.

The fibers useful herein, as described above, may be prepared asdisclosed in U.S. Pat. Nos. 3,375,21 1; 3,375,212; 3,503,907; 3,584,090or 3,381,077. In general, the fibers are made from fiber-forming,organic polymers, especially polymers of ethylene terephthalate or vinylchloride or copolymers predominantly comprising units of either of theforegoing and up to about 10% by weight of units derived from othercompounds copolymerizable therewith.

In general, the fibers are formed by flash extrusion in. which asolution of the polymer in a solvent is maintained at super atmosphericpressure and at atemperature above the boiling point of the solvent. Bycareful adjustment of conditions, as described in said patents, themicrocellular, closed-cell fibers are obtained. The fibers are usuallypost-inflated, i.e., the inflatant is added to the cell interior toprovide the inflated, pneumatic properties of the fiber. This inflationprocedure is also described in the aforementioned U.S. patents.Generally, the fibers contain about 10 or more cells per cc of fiber andwhen inflated have a density of between about 0.008 and 0.05 gm./cc. Inaddition, the inflated fiber diameters can range from about 0.025 to0.25 inch, preferably about .03 to about 0.10 inch.

The anti-adhesive used herein is a surface-active agent, and is apolyoxyethylene polyoxypropylene polymethylsiloxane containing about 51%polyoxyethylene, a sodium alkylsulfonate of 22 to 24 carbon atoms, or apolyoxyethylene polyoxypropylene glycol containing aboutpolyoxyethylene. The polysiloxane can be obtained from Dow-Corning as DC473 fluid; the glycol can be obtained from BASF- Wyandotte as Pluronic".

The anti-adhesive is coated onto the batt, either by dipping the battinto an aqueous mixture containing it, or by spraying it onto theunbonded batt from an aqueous dispersion to a level between about 0.03and 5%, preferably 0.05 and 0.3%, by weight of the antiadhesive based onthe batt. Spray application is preferred for continuous preparation ofthe batts of this invention. The aqueous dispersion may convenientlycomprise 01-03% of the active ingredient. The batt should be sprayedwith water prior to application of the coatings. Wetting aids inapplication of the coating.

The anti-adhesive coating applied need not be dried, although it can beif desired, for the adhesive binder may be applied immediatelythereafter. The adhesive binder is conveniently applied by spraying iton the batt although dipping the batt, while supported between scrims,in a dispersion of the adhesive may be employed. The binder employed isa copolymer of ethylene and vinyl acetate containing 18-40% by weightpolymerized vinyl acetate (preferably 25-30%). Suitable aqueousemulsions of them can be prepared as described in U.S. Pat. No.3,347,811. Preferably, the polymers have molecular weights correspondingto a melt index of less than 50, more preferably from about 1 to about20. (Melt index is determined according to ASTM Dl238-modified). Usuallyabout 15% by weight surfactant is employed to provide storagestabilityto the emulsion. Suitable surfactants include the sodium and potassiumsulfates of straight-chain fatty alcohols containing 10-18 carbon atoms.It is usually applied from a 50% solids aqueous emulsion.

After application of the adhesive binder, the batt is dried, usually at120-150C., under the compression required to develop the desiredcharacteristics.

Preferably the coated batts will contain from about 1 to 1.5 percentanti-adhesive based on weight of fiber and about 5 to about 8 ounces ofadhesive binder per square yard of batt. The invention is furtherdescribed in the following Example which is representative thereof andis not meant to be limiting. In the Example, parts are by weight unlessotherwise noted.

EXAMPLE I Microcellular, closed-cell filaments are preparedsubstantially as described in Example IV in U.S. Pat. No. 3,381,077. Inthis procedure, a solution of a high molecular weight ethyleneterephthalate polymer in methylene chloride is extruded to yieldmicrocellular closed-cell filaments in which the cells are in acollapsed state.

The filaments are cut to approximately 3-inch (7.6 cm) staple andinflated by brief contact with methylene chloride andperfluorocyclobutane and rapid drying to eliminate the methylenechloride (plasticizer) and to trap inside the cells part of theperfluorocyclobutane (to which the cell walls are impermeable in theabsence of the plasticizer).

The inflated filaments are heated in air to about 150C, which furtherinflates the cells by air, yielding microcellular, inflated closed-cellpneumatic fibers having a density of about 0.226 g/cc.

Several batts are made of the fibers by. wetting them with water anddepositing them randomly on a continuous, perforated belt to form aloose batt of about 4 inch (10.2 cm) thickness. In Sample A, noanti-adhesive is employed and the batt sample is used as a control. The

before being released from compression. The resulting batt had a densityof about 0.032 g./cc. and consists of about equal weights of fiber andbinder.

In Samples B and C, the anti-adhesive described in Table 1 was appliedto the batt by adding it to the aqueous emulsion described for Sample Aand applying as described for Sample A. The batts were compressed asdescribed for that Sample.

1n Samples D, E and F the anti-adhesive described in Table I was appliedto the batt by spraying it on from 0.5%, 0.1% and 0.05% solutions,respectively, in water. The aqueous emulsiondescribed for Sample A wasthen applied and the sample subjected tothedrying and compressingdescribed as for Sample A.

' 1n Samples G, H and I, the batts were sprayed with the aqueousemulsion as described for Sample A, and then sprayed with theanti-adhesive described in Table I, as described for Sample D.

Table 1 shows the results when the sprayed batts A-l were tested fortheir noise level by the test described as follows:

A wooden box having the overall dimensions of a lfoot cube with the topopen is used to house a micro phone (Type 15602131, No. 26845). Theoutput of the microphone is fed to a Type l560-P-40 preamplifier, andthence to a Sound-Level Meter Type 1565-A and a Graphic Level RecorderType l52l-B. A Sound- Level Calibrator Type 1562 is employed to assure.a uniform base level for all tests. (The foregoing equip ment ismanufactured by General Radio Co.).

sured and the test reading is corrected for this back- I ground in thetabulation of results.

TABLE I Sample Anti- Wt. On How Added Noise Batt Adhesive Fiber ToSample Batt (db) A None 33 or more B DC-473 (1%) Added to Adhesive 22Emulsion C A\'itone" A (5%) Added to Adhesive 2'1 Emulsion D D0473(0.08%) Sprayed on batt 24 before adding binder E DC-473 (0.40%) Sprayedon batt 16 before adding binder F "Pluronic- (0.80%) Sprayed on batt 18before adding binder G D0473 (0.571) Sprayed on already 30.7

bonded batt H DC-473 (l7r) Sprayed on already 31.4

bonded batt I DC-473 (2'7!) Sprayed on already 32.0

bonded batt DC-473 is a polyoxyethylene, polyoxypropylenepolymethylsiloxane obtainable from the Dow Chemical Company. PluronicF38 is a polyoxyethylene polyoxy propylene glycol obtainable fromWyandotte Chemical Company. Avitone A is a sodium alkylsulfonateobtainable from E. I. du Pont de Nemours and Company.

Subjective evaluation indicates that the noise of flexing becomesobjectionable above the level of about 27 decibels. Thus, as evidencedby the data in Table I, spraying the anti-adhesive onto an alreadybonded batt does not provide adequate reduction of noise level.

The preceding representative examples may be varied within the scope ofthe present total specification disclosure, as understood and practicedby one skilled in the art, to achieve essentially the same results.

The foregoing detailed description has been given for clearness ofunderstanding only and no unnecessary limitations are to be understoodtherefrom. The invention is not limited to the exact details shown anddescribed for obvious modifications will occur to those skilled in theart.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A process for reducing the noise in compressible fibrous-structureswhen flexed under stress, which comprises:

spraying a reticulated batt of randomly arranged, mi-

6 crocellular, inflated closed-cell, pneumatic fibers of a syntheticorganic polymer with between about 0.03 to about 5 percent by weightbased on the weight of the fibers of an anti-adhesive comprising anaqueous dispersion of a compound selected from the group consisting of apolyoxyethylene polyoxypropylene polymethylsiloxane containing about 51%polyoxyethylene, a sodium alkylsulfonate of 22 to 24 carbon atoms and apolyoxyethylene polyoxypropylene glycol containing aboutpolyoxyethylene; coating said sprayed batt with an adhesive bindercomprising an aqueous emulsion of at least 40% by weight of anethylene/vinyl acetate copolymer wherein the vinyl acetate comprises18-40% by weight of the polymer; and drying the coated batt. 2. Theprocess of claim 1 wherein the synthetic organic polymer is polyethyleneterephthalate.

3. The process of claim 1 wherein the anti-adhesive is thepolymethylsiloxane described therein.

4. The process of claim 3 wherein the amount of the I polymethylsiloxanecoated onto the batt is between about 1 and about 5 percent by weight,based on the weight of the fibers.

5. The process of claim 4 wherein the synthetic organic polymer ispolyethylene terephthalate.

1. A PROCESS FOR REDUCING THE NOISE IN COMPRESSIBLE FIBROUS STRUCTUREWHEN FLEXED UNDER STRESS, WHICH COMPRISES: SPRAYING A RETICULATED BATTOF RANDOMLY ARRANGED, MICROCELLULAR, INFLATED COLSED-CELL, PNEUMATICFIBERS OF A SYNTHETIC ORGANIC POLYMER WITH BETWEEN ABOUT 0.03 TO ABOUT 5PERCENT BY WEIGHT BASED ON THE WEIGHT OF THE FIBERS OF AN ANTI-ADHESIVECOMPRISING AN AQUEOUS DISPERSION OF A COMPOUND SELECTED FROM THE GROUPCONSISTING OF A POLYOXYETHYLENE POLYOXYPROPYLENE POLYMETHYLSILOXANECONTAINING ABOUT 51% POLYEXYETHYLENE A SODIUM ALKYLSULFONATE OF 22 TO 24CARBON ATOMS AND POLYOXYETHYLENE POLOXYPROPYLENE GLYCOL CONTAINING ABOUT80% POLYOXYETHYLENE; COATING SAID SPRAYED BATT WITH AN ADHESIVE BINDERCOMPRISING AN AQUEOUS EMULSION OF AT LEAST 40% BY WEIGHT OF ANETHYLENE/VINYL ACETATE COPOLYMER WHEREIN THE VINYL ACETATE COMPRISES18-40% BY WEIGHT OF THE POLYMER; AND DRYING THE COATED BATT.
 2. Theprocess of claim 1 wherein the synthetic organic polymer is polyethyleneterephthalate.
 3. The process of claim 1 wherein the anti-adhesive isthe polymethylsiloxane described therein.
 4. The process of claim 3wherein the amount of the polymethylsiloxane coated onto the batt isbetween about 1 and about 5 percent by weight, based on the weight ofthe fibers.
 5. The process of claim 4 wherein the synthetic organicpolymer is polyethylene terephthalate.